Musical-theater superstar Patti LuPone says shooting her guest-starring role on an episode of Showtime’s horror series “Penny Dreadful” last season wasn’t all fun and games.

She and co-star Eva Green had to skin a rabbit onscreen, and the series’ exacting creator/showrunner, John Logan, made sure they knew what they were doing.

“Eva and I would start our day skinning five or six rabbits,” LuPone tells The Post. “It was disgusting and smelly. And then of course, on the day that we shot that scene, the rabbit was prepped and it wasn’t that difficult to do.”

In that episode, LuPone, 67, played the Cut-Wife, a fright-wigged crone who tutors Green’s Vanessa Ives in the ways of white witchery. She was such a hit as a kind of Yoda of the moors that Logan made her a regular on Season 3 — premiering Sunday at 10 p.m. — as psychologist Dr. Florence Seward.

There was just one hitch: The Cut-Wife had died in Season 2.

“John just wrote another character for me!” LuPone says. “Dr. Seward is totally different: a New Yorker, an independent feminist.”

Seward, a “mental doctor of sorts,” starts treating Vanessa, so once again the two actresses share a close screen relationship. It helped that they instantly clicked in real life.

“Even having just met, we had that elusive chemistry,” LuPone recalls. “We knew we could go the distance with each other. Eva is an incredibly unique and special woman, and it’s reflected in her acting.”

LuPone’s friendship with Logan goes back about six years, when he cast her as a Broadway star in “Miraculous Year,” an HBO pilot that wasn’t picked up. Fast-forward to 2014, when he offered her the Cut-Wife role.

LuPone relishes that casting’s irony, as she was fresh off an arc as a fundamentalist Christian in “American Horror Story: Coven.”

It’s even stranger that it took her so long to land another gig as a regular on a TV series. This is her first regular role since her four-season stint on ABC’s “Life Goes On,” which ended in 1993.

(She’s signed an option for two more years on “Penny Dreadful,” which means Dr. Seward is safe. Maybe.)

Of course, LuPone hasn’t been idle — she’s collected Tony Awards and hit Broadway shows — but her TV appearances have been limited to guest turns. “Years ago, you could kiss a TV show goodbye if you were in the musical theater,” she says. “It’s become a more fluid interchange now.”

And she’s open to appearing in a live musical on TV — if the right people call.